Conventionally, various capacitors have been developed in an attempt to reduce size and increase capacity. Among them, solid electrolytic capacitors are widely known as capacitors fit for size reduction. One kind of a solid electrolytic capacitor includes an anode element comprising: a sintered element comprising a valve metal, examples thereof including niobium, tantalum, and aluminum; or a foil comprising such valve metal and having a surface roughened by etching or the like. Such a solid electrolytic capacitor has an anode element with a large surface area, and therefore has a dielectric film of a wider area. As a result, size reduction and capacity increase are made possible.
In particular, a solid electrolytic capacitor including a solid electrolyte comprising a conductive polymer has a small size, large capacity, low equivalent series resistance (hereafter, “ESR”), and furthermore, excellent features such as being suited for surface mounting. Thus, a solid electrolytic capacitor including a solid electrolyte comprising a conductive polymer is an indispensable element for realizing smaller size, higher performance, and lower production cost for electronic devices.
In an attempt to meet the requirement of size reduction in electronic devices, development efforts are underway to further improve the features of the foregoing solid electrolytic capacitor. For example, Patent Literatures 1 and 2 disclose materials made of a conductive polymer capable of improving performance of a solid electrolytic capacitor, such as conductivity and ESR.